Monographs Details: Mimosa adamantina Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1991. Sensitivae Censitae. A description of the genus Mimosa Linnaeus (Mimosaceae) in the New World. Mem. New York Bot. Gard. 65: 1-835.
Synonyms:Mimosa multiplex Benth.
Description:Species Description - Slender unarmed, erect or assurgent shrubs 630 dm with defoliate annotinous and older trunks scaly with persistent stipules and atrocastaneous lustrous glabrous annotinous branchlets, the dull brown-olivaceous foliage glabrous except for rare random appressed setulae about the pulvini and pulvinuli, the plane thick-textured lfts sometimes vestigially setulose-ciliolate, the globose capitula solitary in the axil of contemporary lvs, at anthesis scarcely emergent and early becoming lateral immersed. Stipules firm erect, linear-attenuate 2-5 x 0.4-0.9 mm, 1-3 nerved, sometimes minutely setulose-ciliolate, persistent. Leafstalks 5-40 mm, rounded dorsally, 2-ribbed but scarcely sulcate ventrally, espiculate; pinnae 1-jug., the rachis 1.5-5.5 cm, the longer interfoliolar segments 1.5-4 mm; lfts 8-14 (-16)-jug., those at each end of rachis a little smaller, the first pair ±1.5-2.5 mm distant from lance-subulate paraphyllidia 0.4-1.1 mm, the blades obliquely lance-oblong or subdimidiately ovate from obtusangulate base, abruptly deltate-apiculate, the longer ones 5.5-10 x (1.7-)2-3.7 mm, (2-)2.2-3.8 times as long as wide, all veinless above, beneath 3(-4)-nerved from pulvinule, the gently incurved midrib dividing blade ± 1:2-2.5, the inner posterior nerve incurved-ascending to beyond mid-blade, the outer posterior ones short or obscure, a weak anterior nerve in some broader blades. Peduncles 1.5—5.5(—7) cm; capitula without filaments 5-6 mm diam., prior to anthesis moriform, the obovoid gray-puberulent 4-keeled fl-buds as long as or longer than bracts, these oblanceolate 1.1-1.6 x 0.4-0.6 mm, glabrous dorsally, minutely ciliolate; flowers 4-merous 4-androus, only some distal ones bisexual; calyx shallowly campanulate 0.25-0.55 mm, the erose rim microscopically ciliolate with filiform or claviform trichomes; corollas narrowly turbinate or the bisexual ones vase-shaped, 2-2.8 mm, the dull purple, concave but not much thickened ovate lobes 0.7-0.9 x 0.6-0.7 mm, externally densely puberulent, especially toward the margins; filaments pink, free to base, exserted 5-8 mm. Pods 1-5 per capitulum, sessile, in profile oblong or narrowly oblong and abruptly cuspidate 12-23 x (4.5-)5-8 mm, 2-4-seeded, the straight or shallowly constricted replum 0.65-1 mm wide, the rather firmly papery valves separating when ripe both from replum and from each other, imperfectly articulate, the endocarp reddish, the exocarp either glabrous or ascending-setose and either smooth or low-venulose; seeds compressed-biconvex ±4-4.3 x 2.8-3.6 mm, the testa dull, brown around periphery, fuscous on faces.
Mimosa adamantina is closely related to M. multiplex, vicariant southward on Sa. do Espinhaço in the latitude of Belo Horizonte. Common attributes are glabrous or nearly glabrous foliage of dull chocolate-brown hue when dried, a minute calyx, and a relatively short broad pod, the ripe valves of which disarticulate imperfectly or not at all. Whereas M. multiplex is essentially herbaceous, its stems arising yearly from the root-crown, M. adamantina is an assurgent or erect shrub, with older defoliate stems giving rise annually to new leafy and fertile branches. Furthermore, the stipules of M. adamantina are on the average narrower and its filaments further exserted from the corolla. The pods of M. adamantina may be either glabrous or pilose with slender ascending setae, whereas those of M. multiplex bear few scattered, grossly dilated conical setae. Like numerous species endemic to the upper levels of Sa. do Espinhaço, M. adamantina has differentiated out into locally endemic variants, two of which deserve varietal status.